diff --git a/README.md b/README.md
index d8b7837..6cddfe0 100644
--- a/README.md
+++ b/README.md
@@ -143,6 +143,11 @@ Secret keys are normalized automatically. The `-` will be `_` and the letters wi
 be converted to upper case (for example a secret with key `secret_key` and
 `secret-key` will become `SECRET_KEY`).
 
+#### Reserved Service Names
+
+Starting with version 3.0, the service name "_chamber" is reserved for chamber's
+internal use. You will be warned when using the service for any chamber operation.
+
 #### Tagging on Write
 
 ```bash
diff --git a/cmd/root.go b/cmd/root.go
index 5eab037..3230d8a 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -117,6 +117,9 @@ func validateService(service string) error {
 	if !validServicePathFormat.MatchString(service) {
 		return fmt.Errorf("Failed to validate service name '%s'. Only alphanumeric, dashes, forward slashes, full stops and underscores are allowed for service names. Service names must not start or end with a forward slash", service)
 	}
+	if store.ReservedService(service) {
+		fmt.Fprintf(os.Stderr, "Service name %s is reserved for chamber's own use and will be prohibited in a future version. Please switch to a different service name.\n", service)
+	}
 
 	return nil
 }
@@ -125,6 +128,9 @@ func validateServiceWithLabel(service string) error {
 	if !validServicePathFormatWithLabel.MatchString(service) {
 		return fmt.Errorf("Failed to validate service name '%s'. Only alphanumeric, dashes, forward slashes, full stops and underscores are allowed for service names, and colon followed by a label name. Service names must not start or end with a forward slash or colon", service)
 	}
+	if store.ReservedService(service) {
+		fmt.Fprintf(os.Stderr, "Service name %s is reserved for chamber's own use and will be prohibited in a future version. Please switch to a different service name.\n", service)
+	}
 
 	return nil
 }
diff --git a/cmd/root_test.go b/cmd/root_test.go
index 276ee27..a09f6c3 100644
--- a/cmd/root_test.go
+++ b/cmd/root_test.go
@@ -51,6 +51,7 @@ func TestValidateService_Path(t *testing.T) {
 		"foo-bar/foo-bar",
 		"foo/bar/foo",
 		"foo/bar/foo-bar",
+		"_chamber", // currently valid, but will be prohibited in a future version
 	}
 
 	for _, k := range validServicePathFormat {
@@ -86,6 +87,7 @@ func TestValidateService_PathLabel(t *testing.T) {
 		"foo/bar/foo:current",
 		"foo/bar/foo-bar:current",
 		"foo/bar/foo-bar",
+		"_chamber", // currently valid, but will be prohibited in a future version
 	}
 
 	for _, k := range validServicePathFormatWithLabel {
diff --git a/store/store.go b/store/store.go
index 3495ff7..f62495c 100644
--- a/store/store.go
+++ b/store/store.go
@@ -6,6 +6,15 @@ import (
 	"time"
 )
 
+const (
+	// ChamberService is the name of the service reserved for chamber's own use.
+	ChamberService = "_chamber"
+)
+
+func ReservedService(service string) bool {
+	return service == ChamberService
+}
+
 type ChangeEventType int
 
 const (
@@ -29,22 +38,25 @@ var (
 	ErrSecretNotFound = errors.New("secret not found")
 )
 
+// SecretId is the compound key for a secret.
 type SecretId struct {
 	Service string
 	Key     string
 }
 
+// Secret is a secret with metadata.
 type Secret struct {
 	Value *string
 	Meta  SecretMetadata
 }
 
-// A secret without any metadata
+// RawSecret is a secret without any metadata.
 type RawSecret struct {
 	Value string
 	Key   string
 }
 
+// SecretMetadata is metadata about a secret.
 type SecretMetadata struct {
 	Created   time.Time
 	CreatedBy string
@@ -59,6 +71,7 @@ type ChangeEvent struct {
 	Version int
 }
 
+// Store is an interface for a secret store.
 type Store interface {
 	Write(ctx context.Context, id SecretId, value string) error
 	WriteWithTags(ctx context.Context, id SecretId, value string, tags map[string]string) error
diff --git a/store/store_test.go b/store/store_test.go
new file mode 100644
index 0000000..ad8ed01
--- /dev/null
+++ b/store/store_test.go
@@ -0,0 +1,12 @@
+package store
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestReservedService(t *testing.T) {
+	assert.True(t, ReservedService(ChamberService))
+	assert.False(t, ReservedService("not-reserved"))
+}